Batch digestion with premixed digestion liquor

ABSTRACT

A batch digesting or pulping apparatus in which a reaction vessel is provided a premixed, reaction liquors mixture predetermined as suitable for the batch-pulping operation. The reaction vessel is connected to supply premixed liquors to a mixing vessel wherein the liquors are intermixed with wood chips; and the wood chips-liquors mixture is pumped to the reaction vessel whereby the chips are sluiced into the latter and the mixture displaces liquors from the reaction vessel. Also, a batch digesting or pulping method wherein a premixed, reaction liquors mixture is supplied to a reaction vessel, then discharged to a mixing vessel in which it is intermixed with wood chips, and the wood chips-liquors mixture is supplied to the reaction vessel to displace premixed liquors therefrom.

United States Patent [72] Inventor Lawrence A. Carlsmith Amherst, NH. [21] Appl. No. 794,023 [22] Filed Jan. 27, 1969 [45] Patented Sept. 2], 1971 [73] Assignee Improved Machinery Inc.

Nashua, NJI.

[ 54] BATCH DIGESTION WITH PREMIXED DIGESTION LIQUOR 9 Claims, 2 Drawing Figs.

[52] [1.8. CI Q. 162/37, 162/52, 162/61 [51] Int. Cl. D2lc [50] Field ofSearch 162/37, 38, 40, 52, 233, 241, 246, 242, 39, 61

[56] References Cited UNITED STATES PATENTS 2,007,348 7 1935 Scharmann et a1. 162/40 x 2,035,447 3/1936 Altick l62/242X Primary Examiner-Howard R. Caine Attorneys-Carl R. Horten, David W. Tibbott and Robert R.

Paquin ABSTRACT: A batch digesting or pulping apparatus in which a reaction vessel is provided a premixed, reaction liquors mixa premixed, reaction liquors mixture is supplied to a reaction vessel, then discharged to a mixing vessel in which it is intermixed with wood chips, and the wood chipsliquors mixture is supplied to the reaction vessel to displace premixed liquors therefrom.

BATCH DIGESTION WITH PREMIXED DIGESTION LIQUOR The present invention relates to batch digesting and more particularly to apparatus and methods particularly adapted for the batch digesting or pulping of wood chips.

Conventionally, in the batch digesting or pulping of wood chips the chips are generally gravity fed into the digester or reaction vessel from either a conveyor system or an overhead storage bin. When a reaction vessel is fed in this manner, however, the chips form into a conical pile which causes a major portion of the chips to lie in a shingled orientation when the reacu'on vessel is full. This shingled orientation of the chips causes channeling of the heat and reaction liquors during the heating and cooking portions of the batch-digesting process and results in nonuniform cooking of the chips and nonuniforrn pulp production. Undercooked portions of the chips result in a substantial quantity of reject chips which must be separated from the acceptable pulp and returned for repulping. Also, the variation in cooking of the chips necessitates that the degree of cooking be more severe than would be necessary with a uniform cook and in this manner reduces the yield of pulp obtained from the chips.

.An object of the invention is to provide a new and improved batch-digesting method particularly adapted whereby a reaction vessel is fed in such a manner that the production of acceptable pulp is facilitated.

Another object is to provide a new and improved batchdigesting method which is particularly adapted for facilitating the control of the mixture of reaction liquors employed during the batch-digesting operation.

In general, these objects are attained by the provision of a batch digesting or pulping method comprising providing a premixed mixture of reaction liquors, supplying the premixed mixture of reaction liquors to a reaction vessel to substantially fill the reaction vessel with the premixed liquors, intermixing the premixed liquors with wood chips externally of the reaction vessel to form a wood chip-liquors mixture and supplying this latter mixture to the reaction vessel to cause displacement of premixed liquors therein while employing displaced premixed liquors to form the wood chips-liquors mixture, cooking the wood chip-liquors mixture in the reaction vessel in a batch cook, and discharging the cooked wood chipliquors mixture from the reaction vessel. Referring to the drawings:

FIG. 1 schematically depicts a batch digesting or pulping apparatus constructed in accordance with the present invention; and

FIG. 2 is a top or plan view illustrating the inlet or upper end of one of the reaction vessels of the digesting apparatus.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout, generally designates a batch digesting orpulping apparatus comprising a plurality of generally vertical or upright, elongated reaction vessels 12 which are all of identical construction. The reaction vessels 12 are each provided with a relatively large diameter, chip inlet 14 adjacent the upper end and chip outlet 16 adjacent the lower end; and the chip inlets 14 are tangentially connected to individual supply pipes 18 each containing a shutoff valve 20. The supply pipes 18, in turn, are connected to a supply manifold conduit or pipe 22 which is provided with a plurality of shutoff valves 23 arranged such that, during the filling of a reaction vessel 12, the portion of the manifold conduit 22 downstream (i.e., to the right in FIG. I) of such vessel 12 may be closed. The chip inlets 14 are provided with chip level probes 25 for sensing when the reaction vessels 12 are substantially filled with chips, such probes 25 being conventional expedients for permitting the vessels l2 to be substantially filled while avoiding the risk of overfilling and plugging.

The chip outlets 16 are individually provided with shutoff valves 24 which control discharge through the chip outlets 16 such that wood chips may be selectively retained in any one or more of the reaction vessels 12 for batch pulping. The chip outlets 16 in the conventional manner are connected through individual discharge pipes 26 to a discharge manifold conduit or pipe 28 communicating with a conventional blow tank (not shown).

The lower ends of the reaction vessels 12 are connected through individual connecting pipes 30, each containing a shutofi valve 32, to a steam supply manifold conduit or pipe 34 which in the conventional manner communicates with a suitable steam source (not shown). The upper ends of the reaction vessels 12 each communicate through a relief pipe 36, containing a shutoff valve 38, with a turpentine extraction or relief manifold 40. In addition, each of the reaction vessels 12 is provided with. a circulating conduit 42 which communicates with the upper and lower ends of its respective reaction vessel 12. Each of the conduits 42 is provided with a control valve 43 and has interposed therein a conventional circulating pump 44 operable to circulate reaction liquors from such respective reaction vessel 12 through the circulating conduit 42. A heat exchanger 81, supplied with steam from the manifold 34 by a conduit 83, may be interposed in the conduit 42 for heating the circulated liquors, if desired. The conduits 42, pumps 44, and heat exchangers 81 are conventional expedients well known in the art and, hence, have been shown in the drawings as applied to only one of the reaction vessels [2 to facilitate the clarity of the drawings.

The apparatus 10 also comprises a liquor accumulator or tank 46 which is of a volume substantially that of a single reaction vessel 12. The accumulator 46 is connected to receive white liquor through a white liquor supply conduit 48 and is also connected to receive black liquor through a black liquor supply conduit 50. The liquor supply conduits 48, 50 are provided with control valves 52, 54, respectively, which during the filling of the accumulator 46 are adjusted to cause the relative proportions of white liquor and black liquor supplied to the accumulator 46 to be such that, after the liquors intermix in the accumulator 46, the accumulator 46 contains a mixture of the liquors predetermined as suitable for the batch-digesting operation to be undertaken. The accumulator 46 is connected to a liquor discharge conduit 56 which communicates with the lower end of each of the reaction vessels 12 through individual liquors supply conduits 60 each containing a shutoff valve 62. A liquors supply pump 58 is interposed in the discharge conduit 56 for supplying the mixture of the liquors through such conduit to the liquors supply conduits 60. A liquors return conduit 63 communicates with the lower end of each of the reaction vessels 12 through individual liquors return pipes 66, each containing a shutoff valve 68, and is connected to the discharge conduit 56 to supply liquors thereto under the control of a valve 70. The liquors return pipes 66, as will be noted, are connected to the reaction vessels 12 to receive liquors through the strainers 64 of such vessels l2; and the before-described circulating conduits 42 communicate with the lower ends of the reaction vessels 12 through such strainers 64 and pipes 66.

The apparatus 10 also includes a mixing vessel or tank 72 which is arranged to be selectively fed dry wood chips by a feed conveyor 74. The mixing vessel 72 may, for example, be of the type disclosed in US. Pat. No. 3,154,295 issued Oct. 27, 1964, to Karl E. Vogel and assigned to the assignee of the present application. The mixing vessel 72 communicates with the liquors return conduit 63 through a branch conduit 76, containing a control valve 78, whereby, during the flow of the liquors through the return conduit 63, a portion of such flow may be directed into the mixing vessel 72 for interrnixture with wood chips therein. The mixing vessel 72 is connected by a feed conduit or pipe to the supply manifold conduit 22; and a feed pump 82 driven by a motor 84 is interposed in the feed conduit 80 for supplying a wood chip-liquors mixture from the mixing vessel 72 to the manifold 22. The feed pump 82 may be of any suitable conventional construction capable of pumping the wood chip-liquors mixture through the feed conduit 80, but preferably is a centrifugal pump.

In the operation of the aforedescribed apparatus 10, the reaction vessels 12 are serially filled from the supply manifold The whole was passed into an oven at 150 C., and kept there for 1-2 minutes. Thereafter, onto the previous layer a second layer (foamed) was spread. which consisted of:

PVC, paste making resin having a K-value of 72 dioctyl phthalate 100 parts (by weight) 80 parts (by weight) The initial thickness of this layer was 200 microns.

The whole was then passed into an oven at 200 C. and kept there for l-2 minutes. The release paper was then removed. The system was then subjected to a slight tension in order to facilitate the separation of those components that were incompatible with each other; then the system was coupled to a cotton jersey fabric (with the second layer adjacent to the fabric), after preliminarily having spread on the fabric some plastisol of the first layer which served as a binder. Said coupling occurred in about 1 minute in an oven heated to ISO-170 C.

The poromeric material thus obtained showed the following air transpiration rates:

Pressure (mm. Hg)

The release paper was then removed and the system was subjected to a slight tension and subsequently was coupled to a jersey fabric made of polyamide fibers, the second layer being adjacent to the fabric after preliminary having spread on the fabric some plastisol of the first layer which serves as a binder.

The poromeric material thus obtained shows the following air transpiration rates:

Pressure cm. of air (mm.Hg) hr. cm.

4U 80 60 121 I00 205 ISO 270 Example 3 100 parts (by weight) PVC, paste making resin with a chip-liquors mixture and pumping this latter mixture to the reaction vessel to provide the batch to be pulped and cause displacement of premixed liquors therein while employing such displaced premixed liquors to form the wood chip-liquors mixture, cooking the wood chip-liquors mixture in the reaction vessel in a batch cook, and blowing the cooked wood chips-liquors mixture from the reaction vessel.

4. A method according to claim 3, wherein the aforegoing steps are cyclically repeated with respect to each of a plurality of reaction vessels.

5. A method according to claim 3, wherein said wood chipliquors mixture is supplied to the reaction vessel by being sluiced in a downward direction into the reaction vessel, and the reaction vessel is supplied the wood chip-liquors mixture at a pressure less than that of the reaction vessel during the cooking of such mixture.

6. A batch-pulping method according to claim 1, wherein only a portion of the displaced premixed liquors is employed 9. A batch-pulping method according to claim 8, wherein said employed portion of the displaced premixed liquors is only a minor portion thereof. 

2. A batch-pulping method according to claim 1, wherein said wood chip-liquors mixture is supplied to the reaction vessel by being sluiced in a downward direction into the reaction vessel.
 3. A method for the batch pulping of wood chips, comprising intermixing a plurality of reaction liquors to form a liquors mixture predetermined as suitable for the batch-pulping operation, supplying the premixed mixture of reaction liquors to a reaction vessel to substantially fill the reaction vessel with the premixed liquors, intermixing the premixed liquors with wood chips externally of the reaction vessel to form a wood chip-liquors mixture and pumping this latter mixture to the reaction vessel to provide the batch to be pulped and cause displacement of premixed liquors therein while employing such displaced premixed liquors to form the wood chip-liquors mixture, cooking the wood chip-liquors mixture in the reaction vessel in a batch cook, and blowing the cooked wood chips-liquors mixture from the reaction vessel.
 4. A method according to claim 3, wherein the aforegoing steps are cyclically repeated with respect to each of a plurality of reaction vessels.
 5. A method according to claim 3, wherein said wood chip-liquors mixture is supplied to the reaction vessel by being sluiced in a downward direction into the reaction vessel, and the reaction vessel is supplied the wood chip-liquors mixture at a pressure less than that of the reaction vessel during the cooking of such mixture.
 6. A batch-pulping method according to claim 1, wherein only a portion of the displaced premixed liquors is employed to form said wood chips-liquors mixture.
 7. A batch-pulping method according to claim 6, wherein such employed portion of the displaced premixed liquors is substantially equal in volume to the volume of the liquors in the wood chips-liquors mixture causing the displacement.
 8. A batch-pulping method according to claim 3, wherein only a portion of the displaced premixed liquors is employed to form said wood chips-liquors mixture, and the remainder of the displaced premixed liquors is utilized to form a portion of the liquors mixture for a succeeding repeat of the process.
 9. A batch-pulping method according to claim 8, wherein said employEd portion of the displaced premixed liquors is only a minor portion thereof. 